1. Field of the Invention
The present invention relates to a recording medium for image formation by an ink-jet recording system, and more particularly to a recording medium suitable for use in a credit card, a bank card, a prepaid card, or the like, an image forming process using the recording medium, and a process for the preparation of the recording medium.
2. Related Background Art
Conventional cards, such as credit cards, bank cards, prepaid cards, etc. contain various information therein. Such information is recorded for example by digitizing the information and recording such information by magnetic recording, or in the form of a bar code, or by so-called optical recording with a laser beam to ablate a part of the optical recording layer or to generate a change in the reflectance thereof or a deformation therein, on a record bearing member, wherein the recording and reproduction of information are achieved by the difference in the optical reflectance or transmittance. There are also utilized an embossing method in which characters and numerals are represented by a protruding part of a card deformed unevenly, and ordinary printing methods such as screen printing or offset printing.
However, the recorded data cannot be read with the human eye in the case of magnetic recording, bar code recording or optical recording of the digitized information. It is therefore not easy to confirm whether the information recorded on the card actually belongs to the holder of the card.
Also, the printing of character information indicating the cautions or regulations for the use of the card and that of logo, background pattern or picture are executed in advance by ordinary printing methods such as screen printing or offset printing. In such printing, however, there are required printing plates corresponding to the number of colors to be printed, and such printing plates cannot be prepared within a short time and become expensive when a small number of cards is to be printed. For this reason, such printing is limited to general information common to a large number of cards, and individual information is currently recorded separately in the form of digital data explained above.
The embossing method, which expresses characters or numerals by means of protruding portions of a card deformed unevenly, allows visual confirmation, but is associated with drawbacks that the amount of information is limited and that such characters or numerals cannot be easily colored. Besides, there is also a drawback that, as such embossing is obtained by deforming the card, the recording area for magnetic or optical recording cannot be provided on such an embossed area.
Recording of individual information, such as a photograph of a face of the card owner, is already adopted in some cards.
However, for example in a method of adhering a photograph itself onto the card, card preparation within a short time is difficult. There is also a problem in a method of printing the photograph directly on the card that the information recording medium may be affected by a surface treatment or printing. Also, a sublimation transfer printing method is associated with a drawback of a high running cost because the ink ribbon is expensive. Further, there has to be selected a base material of satisfactory printability.
For resolving these drawbacks, there has been disclosed a card in which an ink-receiving layer is laminated on a card substrate and on which information is recorded by an ink-jet recording system.
Japanese Patent Application Laid-Open No. 57-784 discloses a card provided, on a card medium, with an ink-receiving layer and further with an ink permeable slidable layer thereon.
However, such medium is defective in safety and in ecology, since the coating liquid contains organic solvent. Also, such a medium is difficult to apply to practical use, because, in a case of using such structure with a polyvinyl chloride substrate ordinarily employed in credit cards, bank cards, etc., the substrate itself is eroded by the solvent to result in a curvature of the card or a cracking of the coated layer.
Japanese Patent Application Laid-Open No. 64-43826 discloses a card in which an ink-receiving layer is laminated on a card substrate and information is recorded by an ink-Jet recording system, but water-fastness and durability of the ink-receiving layer seem to be insufficient.
Japanese Patent Publication No. 3-24906 discloses an ink-receiving layer containing cationic hydrated aluminum oxide, and Japanese Patent Application Laid-Open No. 4-37577 discloses an ink-receiving layer containing alumina hydrate.
Japanese Patent Publication No. 2-31673 discloses an ink Jet recording medium in which an inorganic pigment layer of high ink absorbability is provided on a substrate and further an outermost fine particle layer of thermoplastic organic polymer is laminated subsequently. Also, Japanese Patent Application Laid-Open No. 7-237348 discloses an ink-jet recording sheet in which a porous layer of alumina hydrate is provided on a substrate and an outermost porous polymer layer is laminated thereon. Furthermore, Japanese Patent Application Laid-Open No. 8-2090 discloses a similar card-shaped ink-jet recording medium.
In these media, the outermost porous resin layer is made non-porous by thermal treatment after ink-jet recording has been conducted. Stated differently, the image formation or absorption and fixation of ink are effected in the inorganic pigment layer composed for example of porous alumina hydrate, and water fastness and durability are achieved by the porous resin layer which has been rendered non-porous.
However, the inorganic pigment layer composed for example of porous alumina hydrate is insufficient in flexibility, and, when such layer is applied to the substrate for example of polyvinyl chloride mentioned above, there will result a drawback that the ink-receiving layer is peeled off by the deformation in embossing. Also, in case of an ink-jet recording system employing a pigment as the coloring material of the ink, the pigment particles constituting the coloring material do not intrude into the ink-receiving layer, which results in insufficient friction resistance of the obtained image. Furthermore, as polyvinyl chloride has a softening temperature as low as 60xc2x0 C. to 80xc2x0 C., there has not been disclosed any effective method for preventing the deformation of the substrate due to the heat treatment for preparing the recording medium or for rendering the outermost porous resin layer non-porous.
An object of the present invention is to provide an excellent recording medium causing no deformation.
Another object of the present invention is to provide an image forming process for forming an image by a simple method on the above-mentioned recording medium.
Further, still another object of the present invention is to provide a process for the preparation of a recording medium causing no deformation.
The above objects can be achieved by the present invention described below.
According to the present invention there is provided a recording medium provided with an ink-receiving layer on at least one surface of a substrate, wherein the ink-receiving layer is a porous layer comprising pigment particles and mutually fused thermoplastic resin particles.
According to the present invention there is also provided an image forming process comprising the step of forming an image by ejecting an ink by an ink-jet recording method onto the above-mentioned recording medium.
According to the present invention there is still further provided a process for the preparation of a recording medium comprising the steps of applying to a substrate a coating liquid comprising pigment particles and thermoplastic resin particles and forming an ink-receiving layer by fuse-gathering the thermoplastic resin with heat under pressure.
According to the present invention there is further provided a process for the preparation of a recording medium comprising the steps of applying to a substrate a coating liquid comprising pigment particles and thermoplastic resin particles; and forming an ink-receiving layer by fusing and adhering the thermoplastic resin with heat under pressure.